During the freezing of a solution at its freezing point,which of the following equilibria exists?

• A
  Solution$_{(l)}$ $\rightleftharpoons$ Solid solution$_{(s)}$
• B
  Solvent$_{(l)}$ $\rightleftharpoons$ Solvent$_{(s)}$
• C
  Solution$_{(l)}$ $\rightleftharpoons$ Solute$_{(s)}$ + Solvent$_{(l)}$
• D
  Solute$_{(l)}$ $\rightleftharpoons$ Solute$_{(s)}$